Operators currently have two solutions to overcome this deficiency. They can withdraw the safety valve from the production tubing (after setting an air lock at the wellhead) and then close the defective control line by setting in the tubing an isolating sleeve provided with packers which isolate the control fluid arrival through the nipple. The well can produce again but it is then outside the safety standards since it is no longer equipped with a subsurface safety valve. Another solution allowing to avoid this off-standard operation consists in “killing” the well, i.e. in balancing the pressure of the reservoir with a hydrostatic mud column of suitable density, then in carrying out servicing operations in the well to repair according to the techniques used in the trade. This solution, which afterwards allows to work according to the safety standards, is extremely heavy and expensive.
Document FR-2,734,863 describes a method and a device allowing to restore well safety by setting, according to the standards in use in the trade, a special safety valve. However, the technique according to this document requires running out the defective subsurface valve and re-using its nipple for installing the special valve. The method thus requires a precise depth for fastening the new valve, considering the re-use of the nipple for its locking system and sealing.
The present invention relates to a well safety valve comprising improvements in relation to the special valve and the tools as described in the aforementioned document FR-2,734,863. The present valve according to the invention can be set directly in the inner space of a production tubing of known inside diameter, without requiring an adapted nipple. Thus, the length of the connecting rods between the valve and the wellhead at the surface no longer has to be adjusted.